Definition of Raynaud's phenomenon

Raynaud's phenomenon: A condition resulting in
discoloration of fingers and/or toes when a person is exposed to
changes in temperature (cold or hot) or emotional events.

The skin discoloration occurs because an abnormal spasm of
the blood vessels causes a diminished blood supply. Initially, the
digits involved turn white because of diminished blood supply, then
turn blue because of prolonged lack of oxygen and finally, the blood
vessels reopen, causing a local "flushing"
phenomenon, which turns the digits red. This three-phase color
sequence (white to blue to red), most often upon exposure to cold
temperature, is characteristic of Raynaud's
phenomenon.